The long-term effects of in utero exposure to organochlorine compounds is of great potential importance. These compounds, which are detectable in essentially 100% of humans worldwide, have been linked to reduced neurodevelopment in children. In addition, p,p'-DDE, the primary metabolite of DDT, is a weak estrogen, and an androgen receptor blocker at concentrations observed in humans. The purpose of this project is to determine whether maternal serum concentration of DDE, obtained during pregnancy, is a risk factor for cryptorchidism, hypospadias and polythelia in male offspring. These malformations were chosen because they are markers of deficient androgen activity in utero. This study will also evaluate the relationship between in utero exposure to PCBs and suboptimal muscle tone, reflexes, IQ and hearing during childhood. Work to date has demonstrated that these compounds can be recovered from the study population at relevant concentrations, and that the correlation between concentrations of these compounds in first and third trimester serum is sufficiently high to employ third-trimester serum as a surrogate for first-trimester exposure.